Data Sources and Calculations

Department of Energy (DOE): Where available, the U.S. DOE is the source of the data and calculations for GHG and MPG.

  • GHG Data: GHG, or "Annual Emissions (lbs. CO2)," is available on the DOE website based on the year, make and model of individual vehicles. GHG information was gathered from the DOE website for all available light-duty vehicles in FAMS based on individual years, makes and models in the fleet.

  • MPG Data: Where GHG is available, the MPG is calculated based on the GHG, using the equation below:

    MPG = miles / gallon

    The table below provides the assumptions needed to calculate the MPG based on the GHG.

    Value or Equation
    Annual Driving Distance
    U.S. DOE
    GGE converted from GHG
    AvgGHG / 24
    GHG to GGE Conversion Factor
    U.S. DOE
    Average Fleet GHG
    TF_GHG / Vehicles
    Sum Total GHG for Fleet
    GHG1 + GHG2 + ...
    U.S. DOE, FAMS, Calculation
    Total Count of Fleet Vehicles
    Vehicle 1 + Vehicle 2 + ...
    FAMS Where GHG is unavailable from the DOE website, the MPG for the vehicle (based on the year, make and model) is available from Based on the MPG provided by, a vehicle’s GHG can be calculated using the same methodology – performed in reverse – that determines a vehicle’s MPG based on its GHG found on the DOE website.

FAMS: This is the data source for fleet data and fuel consumption.

  • Fleet data: Departments are required to report fleet data on a regular basis pursuant to California Public Resource Code (PRC) Section 25722.5.

  • Fuel consumption: Fuel data is captured in FAMS and validated by departments. Note that the fuel amounts in FAMS for E85 and biodiesel have been adjusted to account for the distribution of petroleum in these alternative fuels (the graphs with alternative fuel reflect only the pure ethanol or biodiesel from the consumption of E85 and biodiesel fuels; the petroleum and diesel is included the appropriate petroleum fuels).

Fleet Focus: This is the database used by DGS Fleet Operations to track leased asset data and is the source used to determine the appropriate DGS lease customer department’s asset count and fuel amount.